Fornacite, Chrysocolla, Baryte Weight: 95.6 g Locality: Moon Anchor Mine, Wickenburg, Arizona, USA — Photo: HolDu · CC BY-SA 3.0 de
Fornacite
A rare green-to-yellow lead-copper chromate-arsenate forming a series with vauquelinite.
Intro adapted from Wikipedia (CC BY-SA).
Fornacite is an IMA-recognized mineral species in the arsenate class, with the chemical formula CuPb₂(CrO₄)(AsO₄)(OH).
It crystallizes in the monoclinic crystal system (space group P2_1/c). It is a member of the Fornacite structural group.
Key properties: Mohs hardness 2.5; specific gravity 6.27; typically green or yellow; Saffron-yellow streak; Vitreous luster; refractive index 2.193; optically biaxial.
IMA symbol For, grandfathered status — known before the IMA’s founding, named in 1915.
A rare mineral found in the oxidized zones of some hydrothermal base-metal deposits.
It is found associated with Dioptase, wulfenite, hemihedrite, phoenicochroite, duftite, mimetite, shattuckite, chrysocolla, hemimorphite, willemite, fluorite.
In honor of Lucien Louis Forneau (1867–1930), Colonial Governor of the French Congo.
Collections: Collector Favorites, Rare & Remarkable.